WASHINGTON — A U.S. senator remains steadfast in blocking the nomination of Air Force Lt. Gen. Susan Helms, tapped to serve as vice commander of the U.S. Space Command, over serious concerns with Helms' decision to overturn a jury conviction in a sexual assault case.

Sen. Claire McCaskill, D-Mo., who first put a hold on the nomination in April, said she met with Helms and Air Force officials yet still had reservations.